|
【范围】
|
The emerging ultra high bypass ratio ADP engines, with nozzle pressure ratios significantly lower, and bypass ratios
significantly higher, than those of the current turbofan engines, may present new in-flight thrust determination challenges
that are not specifically covered in AIR1703. This document addresses candidate methods and the additional challenges
to the thrust determination for these ADP engines.
These novel challenges result in part from the fact that some large ADP engines exceed present altitude test facility
capabilities. The traditional methods of nozzle coefficient extrapolation may not be most satisfactory because of the
increased error due to the ADP higher ratio of gross to net thrust, and because of the increased sensitivity of in-flight
thrust uncertainty at the lower fan nozzle pressure ratio. An additional challenge covered by this document is the higher
sensitivity of ADP in-flight thrust uncertainty to the external flow field around the engine, and the changes in this flow field
due to aircraft configuration and operations.
Calibrations for in-flight thrust determination for these ADP engines may have to be based on other alternate methods.
Recently, large size turbo powered simulators (TPS) of propulsion systems (including the nacelle) have been developed
and thus provide a new capability for in-flight thrust determination. Furthermore Computational Fluid Dynamic (CFD)
analysis may prove to be a viable supplement to ground (sea level) engine testing and sub-scale model coefficient
extrapolations to cruise conditions. These recent developments are described within along with their associated error
assessments.
The candidate thrust methods build on the work presented in AIR1703. The document includes a comprehensive
uncertainty assessment conducted per AIR1678 to identify the major thrust determination options. Fundamental to this
uncertainty assessment are the influence coefficients relating in-flight thrust calculation uncertainty to the measured
parameters and derived coefficients. These influence coefficients were developed from three typical public domain,
generic engine cycle models.
For the major potential thrust determination options, the overall thrust and airflow calibration processes are defined in
detail. Road maps are included showing model, engine and flight-tests, measurements and correlations, calibration
procedures and analyses. The document addresses the pros and cons of each of the major thrust determination options,
including a discussion of the key assumptions and expected uncertainties.
1.1 Document Roadmap
The following schematic shows how to use this document. The type of thrust method used is dependent on several
factors such as: the nature of the program itself and whether it’s a new aircraft and engine or a re-engine program; the
performance and guarantee requirements; the thrust accuracy required; the available budget; the power management
parameter; etc.
Sections 3 through 5 provide methodology and background information relevant to the challenges of integrating an ADP
propulsion system into an aircraft. The key engineering activity to determine the validated in-flight thrust performance is
focused in Sections 6 through 9.
{200a009d9872dccb15c382be6ead36f4.jpg}strRefField
|